1. Field of the Invention
The present invention relates generally to computer systems, and more specifically to a computer system having a universal serial bus (USB) interface. In particular, the present invention allows a computer system to be activated in response to activity generated at a universal serial bus peripheral.
2. Description of the Related Art
Universal serial bus has been developed to provide a uniform electrical interface for personal computer system peripherals. As a result, peripherals, such as pointing devices, joysticks, modems, and Local Area Network (LAN) adapters equipped with a universal serial bus interface, have easier connection and lowered interface cost. Currently, up-to-date universal serial bus interfaces are developed in accordance with universal serial bus specification Revision 2.0 as promulgated by universal serial bus Implementers Forum, Inc., an Oregon non-profit corporation formed by a consortium of manufacturers of universal serial bus-related components.
Universal serial bus uses a hub-based interconnect, that provides a star configuration interconnect in order to interface a potentially large number of peripherals to the main processing unit of a computer system. Hubs are used to provide an individual port for each peripheral or to provide a port for connection to another hub. Power and data signaling are incorporated within a single cable, making peripheral interfaces so convenient that wall adapters for low-power peripherals may be eliminated, and a single cable connection can be made.
Present-day computer systems provide power management to conserve power and reduce heat generated by a computer system when system activity is not required. A computer system may be set to a totally shutdown state, or may be placed in various modes known as “suspend” or “resume”, among other terms of art used to describe an operating mode in which a portion of the computer system is active waiting on a stimulus to resume full system operation. Examples of stimuli that can be detected for resuming operations are mouse movement, modem dial-in, and LAN activity.
The universal serial bus specification provides a power management feature whereby a connected universal serial bus peripheral may wake up a host computer system using a resume signaling protocol. This power management feature may only be used while universal serial bus peripheral devices are placed in a suspended mode. Since the suspended mode must be initialized by the universal serial bus software components provided by the operating system, the universal serial bus peripheral device must be connected and the operating system must be executing on the host system prior to the use of the universal serial bus peripheral to wake up the system. Thus, the wake-up feature typically cannot be used with an uninitialized device that has not been connected to the host system prior to the host system entering the suspend state. Additionally, the resume signaling mechanism provides only a simple on/off signaling with no security provision for controlling power management access.
Therefore, it would be desirable to provide an improved method and apparatus for activating a computer system in response to a stimulus from a universal serial bus peripheral.